Cost-effectiveness analysis of therapy for symptomatic carotid occlusion: PET screening before selective extracranial-to-intracranial bypass versus medical treatment

The St. Louis Carotid Occlusion Study (STLCOS) demonstrated that increased cerebral oxygen extraction fraction (OEF) detected by PET scanning predicte d stroke in patients with symptomatic carotid occlusion. Consequently, a tr ial of extracranial-to-intracranial (EC/IC) arterial bypass for these patie nts was proposed. The purpose of this study was to examine the cost-effecti veness of using PET in identifying candidates for EC/IC bypass. Methods: A Markov model was created to estimate the cost-effectiveness of PET screenin g and treating a cohort of 45 symptomatic patients with carotid occlusion. The primary outcome was incremental cost for PET screening and EC/IC bypass (if OEF was elevated) per incremental quality-adjusted life year (QALY) sa ved. Rates of stroke and death with surgical and medical treatment were obt ained from EC/IC Bypass Trial and STLCOS data. Costs were estimated from th e literature. Sensitivity analyses were performed for all assumed variables , including the PET OEF threshold used to select patients for surgery. Resu lts: In the base case, PET screening of the cohort followed by EC/IC bypass on 36 of the 45 patients yielded 23.2 additional QALYs at a cost of $20,00 0 per QALY, compared with medical therapy alone. A more specific PET thresh old, which identified 18 surgical candidates, gained 22.6 QALYs at less cos t than medical therapy alone. The results were sensitive to the perioperati ve stroke rate and the stroke risk reduction conferred by EC/IC bypass surg ery. Conclusion: If postoperative stroke rates are similar to stroke rates observed in the EC/IC Bypass Trial, EC/IC bypass will be cost-effective in patients with symptomatic carotid occlusion who have increased OEF. A clini cal trial of medical therapy versus PET followed by EC/IC bypass (if OEF is elevated) is warranted.